Closes #11

• Added a specific CONTRIBUTING.md file (previously we just linked to the organisation one)
  • Updated the README.md to reflect his
• Added a simple Issue template, suggestion.md
• Removed the welcome banners from config.yml for now, because they do not render
• Added workflow auto-author-assign.yml - this automatically makes the author of an Issue or PR the Assignee slot (it can be manually changed, but this ensures Issues and PRs to always have an Assignee, helping with project boards and other GH filters which read this Assignee slot)
• Added workflow auto-label.yml - this automatically labels PRs with a certain label (defined in labeler.yml) depending on what file was edited. Helps to automate project management. Only a few files are listed in labeler.yml or now - can be expanded.

You can see some of these workflows in action in this PR: aim-rsf/browseMetadata#105